It is known that composite materials are, for the most part, constituted of reinforcing fibers dispersed in a suitable matrix; the reinforcing fibers which are used are organic or inorganic fibers such as Nylon fibers (aromatic or non-aromatic), carbon fibers, glass-fibers, silicium carbide fibers, boron fibers, etc. The matrices used are also of organic or inorganic nature, such as for example resin. Moreover, these matrices can contain various fillers such as for example: graphite powder, titanium powder, ceramic powder, etc. The materials according to the invention contain fibers and matrices such as described hereinabove.
Composite materials may be mono-, bi- or tri-dimensional in their properties, depending on the orientation or orientations of the fibers.
It is known to produce mono-directional, i.e. parallel fibers held by fine Nylon yarns or glass yarns, etc., or bi-directional composite materials constituted of a plurality of mono-directional layers, stacked and forming different angles between them, or just simply woven. But to produce a tri-dimensional structure, the problem is more complex. All the known processes make use of a special knitting, or of fibers which traverse bi-dimensional assemblies, each fiber being guided by a needle. Certain types of felts, are also used, which are known as tri-dimensional felts and which are no more no less than the conventional knitted pile fabric type.
But it is also known that the properties of the obtained materials can be dependent on the regularity of dispersion and on the orientation of the fibers and that there is an advantage in finding a process whereby such dispersion and orientation in the various directions required, can be accurately controlled. This is precisely the object of the present invention.